The field of the invention is that of pressure sensors having capacitive pressure transducers and the invention relates more particularly to a pressure sensor having a pressure responsive capacitive pressure transducer mounted on a housing with a signal conditioning electrical circuit which is calibratable relative to the transducer after mounting on the housing.
A known pressure sensor as shown in U.S. Pat. No. 4,716,492 comprises a capacitive pressure transducer having a thin ceramic diaphragm mounted in closely spaced, sealed, overlying relation to a ceramic base, and having metal coatings deposited on respective opposing surfaces of the diaphragm and base to serve as capacitor plates arranged in predetermined closely spaced relation to each other to form a capacitor. Transducer terminals connected to the capacitor plates are arranged at an opposite surface of the transducer base and a signal conditioning electrical circuit connected to the transducer terminals is mounted on the transducer. A cup-shaped connector body of electrical insulating material is fitted over the electrical circuit and is secured to the transducer by a metal housing sleeve which has a port for exposing the transducer diaphragm to an applied pressure and which has a rim deformed against the connector body. In that arrangement, the diaphragm is movable in response to variation in pressure applied to the diaphragm to vary the capacitance of the capacitor in accordance with the changes in applied pressure and the electrical circuit provides an electrical output signal corresponding to the applied pressure. The electrical circuit is calibratable relative to the capacitive pressure transducer after mounting in the sensor housing so that the sensor is adapted for wide application to be suitable for low cost high volume manufacture. It is somewhat difficult to assemble the sensor in an economical manner, to properly calibrate the sensor and seal it after calibration, and to assure that the sensor is compatible with use in automotive environments and the like where there is substantial electromagnetic interference.